1. Field of the Invention.
This invention relates generally to fasteners of various kinds and relates particularly to a hardened nail having a penetrating portion that may be driven into a structural metallic member and a portion of the nail deforms to attach the nail to the member in a manner to resist withdrawal.
2. Description of the Prior Art.
In the past many efforts have been made to provide fasteners such as nails, screws, rivets and the like which could be driven, screwed or inserted into openings in a base material. Most of these prior art fasteners retain their shape with the exception of rivets in which one end is peened over after the rivet has been inserted in a preformed hole. Additionally, some nails have been provided with bifurcated shanks in which the shanks spread apart when the nail is driven into a relatively soft somewhat resilient base material such as wood or the like.
Some prior art structures, such as the patent to Anderson 1,349,183, have included a hollow tubular pin or shank which is adapted to be driven into a wood base material and the penetrating end of the pin is of a configuration to deform slightly to prevent easy withdrawal. However, structures of this type which are to be driven into wood normally include a sharp cutting edge which severs the fibers of the wood.
The prior art patent to Walker U.S. Pat. No. 3,699,636 discloses a hard metallic tubular member the penetrating end of which is provided with a pair of tapered chamfer portions so that the tubular member may be driven into a softer base material to cause the base material to be deformed while the penetrating portion retains its original configuration.
Also some prior art nails such as the patent to Hermle U.S. Pat. No. 3,555,957 have been provided with a hardened penetrating point which could be driven into a hard dense metallic base material by means of an explosive charge. However, the penetrating portion of the fastener is not intended to deform as it is driven.
Some fasteners, such as my U.S. Pat. Nos. 3,871,264 and 4,004,483, have been provided that can be driven into a hard dense metallic structural member in which the penetrating portion of the fastener is harder than the base material and is of a configuration such that the penetrating portion of the fastener retains its shape while portions of the base material are adapted to be deformed into recesses in the fastener for locking the fastener to the base material.
Success was obtained with clinch type fasteners which could be driven into relatively soft sheet metal or the like as disclosed in my prior U.S. Pat. Nos. 3,095,777 and 4,003,286, but in the absence of certain critical parameters, there was no evidence that they would function properly in hardened structural steel. The disclosure in my U.S. Pat. No. 3,095,777 included several embodiments, however, the main thrust of the disclosure was toward driving the fastener into relatively soft sheet metal. The flow characteristics of relatively soft sheet metal are substantially different from the flow characteristics of relatively hard, thick structural metal since material which is displaced in sheet metal tends to flow downwardly and toward the side, while the displaced material of the structural metal tends to flow upwardly. When the sheet metal rests on an anvil, the metal tends to flow toward the side only. Accordingly the physical dimensions of a fastener for driving into sheet metal are not as critical as the dimensions of a fastener for driving into hard structural metal. For example, it has been determined that the width of the blunt point has a direct relationship with the diameter of the bore, that the hardness of the penetrating end has a direct relationship with the hardness of the metallic structure, and that the pressure on the penetrating end of the fastener is substantially greater when the fastener is driven into a structural metallic member than when driven into sheet metal.